On a different note

Iirc the name is kinda like passed down from kin to kin (it's more complex than that though), the dantallion family is based on the goetic demon known as dantalion (also) a goetic demon known for having many kinds of faces (men and women alike)so it's the way this manga symbolizes the dantalion demon themselves, which is having the demons in the dantallion family named the same to symbolize having many kinds of faces

Someone correct me if I'm wrong though :DD

Yes and he's probably the son